1) I find it easier to break it down into smaller chunks:
0.01 (AKA 1%) x 1000 = 10. 2000 ÷ 2 = 1000, therefore, 10 x 2 = 20. There are 20 defective lightbulbs in the shipment. 2000 - 20 = 1980 working bulbs.
2) 50% x 20% = 10% x 20% = 2%. The jacket is now at 2% the original price. (I wish that were actually true)
3) Think about it this way: 500 x 25% = 125. Because 496 is 4 less than five hundred, 4 x 25% = 1, therefore 25% of 296 is 124. 496 - 124 = 372 ÷ 12 = 31. Each payment was $31.00